Clamp for holding strip material on pad



y 1956 o. BURKART CLAMP FOR HOLDING STRIP MATERIAL 0N PAD Filed Oct. 6, 1954 GWEN BURKHRT INVENTOR.

ATTORNEY United States Patent G CLAMP FOR HOLDING STRIP MATERIAL N PAD Owen Burkart, Andrews, Ind.

Application October 6, 1954, Serial No. 460,545

7 Claims. (Cl. 51-189) This invention relates to a clamp for holding strip material such as sand paper, emery cloth, etc. on a pad, particularly a pad which is used with an orbital sanding machine.

It is a well known fact that the individual strips of abrasive material held on the pad are worn out rather rapidly so that, to lengthen the period of productive operation between reloadings 'of the pad with new strips, the operators try to load the pad to capacity.

Since the operation of the machine causes the application of relatively strong forces which tend to pull the strips from under the clamping means, it usually occurs that a number of strips, usually from 1 to 4, pull out from the clamp and must be torn off and are wasted. The length of the production cycle is therefore considerably shortened, since from 6 to 12 strips are initially loaded. The waste of strips also constitutes a considerable loss of money.

It is, accordingly, an object of the invention to provide a clamp which will hold the strips securely on the pad.

Another object of the invention is to provide a clamp which will hold many strips, securely.

Yet another object of the invention is to provide a clamp which is inexpensive and which can be applied to existing pads.

Still another object of the invention is to provide a clamp which is easy to manufacture.

A further object of the invention is to provide a clamp which is easy to load and operate.

Yet another object of the invention is to provide a clamping means which will tension the strips of abrasive material and'hold them closer to the felt to reduce friction between the sheets and to prevent deterioration of the sheets which are not in use, during operation and to reduce deterioration of the resilient body material.

Still another object is to reduce wear on the bearing portion of the actuator due to vibration.

These and other objects will become apparent from a study of this specification and the drawings which are attached hereto, made a part hereof and in which:

Figure 1 is a plan view of a pad with the clamps arranged one in receiving and one in clamped position.

Figure 2 is an elevation of Figure 1 with a portion shown in section to illustrate the clamping action.

Figure 3 is a sectional view taken substantially on the line 3-3 of Figure 1 to show the mounting for the clamp actuator.

Figure 4 is a side elevation of the mechanism showing the clamp in the position of entering the actuator.

Figure 5 is a plan view of the clamp.

Figure 6 is a side elevation of the clamp.

Referring particularly to Figures 1 to 4 of the drawings, the numeral 1 represents the pad, generally, which comprises a base 3 made of sheet metal having down turned ends 5 and sides 7 which serve to retain a body 9 of resilient material such as felt, which serves as a yieldable support for the strips 11 of abrasive material.

A suitable connector 13 is aflixed to the base 3 to at- 2,746,215 Patented May 22, 1956 '2 tach the pad to the machine which is represented by the dashed lines in Figure 2.

Mounted on the top of the base 3 by means of :rivets 15 are the bearing clips 17 which are relatively stifi, but will bend slightly so that an actuator 19 which has .its journal 21 mounted under the bearing portion 23 of the associated clip (see Fig. 3) will be urged toward contact with the base 3 and will be rotatable in the clip. A-.s1ot 25 is provided in each end of the actuator for the reception of a screw driver.

The ends 27 of each actuator which extend beyond the clips are of polygonal form. They are here shown as being hexagonal.

The structure thus far described is conventional and the intended method of operation is to insert 'the ends of a number of strips :11 of abrasive material directly under the polygonal portions 27 of the actuator and then, by rotating the actuator with a screw driver, work the ends of the strip under the actuator into clamping position. A similar operation is performed with the opposite ends of the strips which are drawn in until the strips are relatively taut on the resilient material 9.

To eliminate the difliculties which are experienced with this loading operation and structure, I have formed a clamp 31 such as that shown, particularly in Figures 5 and 6 which comprises a straight clamping bar 33 at the ends of which the wire is bent 180 degrees at 35, on a radius which is approximately equal to the wire diameter so that 'a space 37 is provided between the parallel runs 38 and the bar to receive the ends of the strips.

The two ends of the wire are then bent at 41, degrees away from the clamping bar but in the same plane as that established by 'the parallelruns and the bar, to form arms 39 which have their terminal portions flattened and tapered on the top and bottom sides, as shown at 43, to facilitate entry of the arms between the polygonal portions of the actuators and the base.

The wire used for the clamp is preferably of about 12 gauge'and soft enough so that, as the actuator is rotated, the corner angles of the polygonal portions 27 will indent the arms 39, as shown at 45 in Figures 1 and 2 and in efiect make of the arms, racks which mesh with them. I have found that a wire made of half-hard aluminum is satisfactory. The Wire must have sufiicient stiffness to retain its shape substantially so that the ends of the strips will be clamped against the base 3 at the edge formed by the juncture of the base 3 and the end 5 as shown on the right hand sides of Figures 1 and '2.

While the strips are to be loaded into the clamp, the latter is moved out beyond the end 5, as shown on the left hand ends of Figures 1 and 2, by suitable rotation of the associated actuator. After insertion of the strips between the clamping bar and the end 5, opposite rotation of the actuator will cause the bar to move toward the end 5 and be drawn into clamping position on the strips.

It will be seen that the insertion of the strips is thus greatly facilitated. Further, the clamping pressure is applied in a direction which is substantially normal to the plane of the strips so that there is little opportunity for the ends of the strips to escape the clamping bar while it is being drawn up or after it has been tightened. Further, the number of strips which can be inserted is increased. It is not uncommon for an operator to insert 16 strips of abrasive and hold them all securely enough so that none are wasted during the operation.

The clamp may be repeatedly operated to insert new strips. Eventually however, the clamping bar, which is in contact with the abrasive surface of the outer strip becomes worn and weakened and it is necessary to install a new clamp. The clamp is very inexpensive and the replacement cost is minute compared with the savings occasioned by the elimination of waste of abrasive paper.

I Of course, if the clamp material is not soft enough to be forged into conformity with the actuator ends, such conformation will have to be otherwise provided before insertion of the clamp between the actuator and the plate.

It is obvious that various changes may be made in the form, structure and arrangement of parts without departing from the spirit of the invention. Accordingly, applicant does not desire to be limited to the specific embodiment disclosed herein primarily for purposes of illustration; but instead, he desires protection falling fairly within the scope of the appended claims.

What I claim to be new and desire to protect by Letters Patent of the United States is:-

1. In a sanding pad which comprises a base plate terminating in an end against which strip material may be clamped, an actuator mounted on the base plate for rotation about an axis which is substantially parallel with said end and said base plate and disposed in closely spaced relation with said plate, said actuator comprising end portions having non-circular cross-sectional conformation, the improvement which comprises a clamp including a bar disposed substantially parallel to the end of the base plate, arms extending from the bar between the base and said end portions of the actuator and coacting therewith to be moved thereby so as to move said bar toward and from said end as said actuator is rotated in one direction or the other.

2. In a sanding pad which comprises a base plate terminating in an end against which strip material may be clamped, actuators rotatably mounted on the base plate, said actuators comprising end portions having non-circular cross-sectional conformation, the improvement which comprises a clamp including a bar disposed substantially parallel to the end of the base plate, arms extending from the bar between the base andsaid end portions of the actuator, said arms being of indentable material so that the actuator as it is rotated, will forge the arms into substantial conformity with the contour of the end portions whereby rotation of the actuator will move the bar toward and away from clamping relation with respect to the end of the base.

3. In a sanding pad which comprises a base plate terminating in an end against which strip material may be clamped, actuators rotatably mounted on the base plate, said actuators comprising end portions having non-circular cross-sectional conformation, the improvement which comprises a clamp including a bar disposed substantially parallel to the end of the base plate, arms extending from the bar between the base and said end portions of the actuator, said arms being of identable material having wedge-shaped ends disposed to enter between the base plate and said end portions so that the actuator as it is rotated, will forge the arms into substantial conformity with the contour of the end portions whereby rotation of the actuator will move the bar toward and away from clamping relation with respect to the end of the base.

4. In a sanding pad which comprises a base plate terminating in an end against which strip material maybe clamped, actuators rotatably mounted on the base plate, said actuators comprising end portions having non-circular cross-sectional conformation, the improvement which comprises a clamp including a bar disposed substantially parallel to the end of the base plate, arms extending from the bar between the base and said end portions of the actuator, said arms being of half-hard aluminum wire so that the actuator, as it is rotated, will forge the arms into substantial conformity with the contour of said end portions whereby rotation of the actuator will move the bar toward and away from clamping relation with respect to the end of the base.

5. In a sanding pad which comprises a base plate terminating in an end against which strip material may be clamped, actuators rotatably mounted on the base plate, said actuators comprising end portions having non-circular cross-sectional conformation, the improvement which comprises a clamp including a bar disposed substantially parallel to the end of the base plate,-the ends of said bar being connected by parallel runs, spaced from the bar, two arms extending away from the bar, said bar and runs defining a slot for the reception of strip material, said arms being entered between saidbase and the end portions of the actuators and having a conformation substantially interfitting with the conformation thereof so that rotation of the actuator will move the clamp bar toward and from'clamping relation with respect to the end of the plate. a

6. The structure defined by claim 1 wherein the crosssectional conformation of the actuator end portions is polygonal.

7. A clamp for a sanding pad which comprises a clamping bar, a pairof arms connected with said bar, disposed inwardly from the ends of the bar, so that the distance between the arms, measured along the bar, is less than the length of the bar, and extending in a direction away from the bar and having free ends opposite the ends which are connected with the bar, said bar and'arms being substantially co-planar, the free ends "of said arms being wedge-shaped to facilitate mounting of the bar.

References Cited the file of this patent UNITED STATES PATENTS 1,179,297 Fisher Apr. 11, 1916 2,256,098 Mauldin Sept. 16, 1941 2,475,476 Champayne July 5, 1949 2,688,827 Hobday Sept. 14, 1954 FOREIGN PATENTS 350,615 Germany June 9, 1914 

